What's Going On Around Saturn? (Part 2)

Although it is no longer uncharted land, the origin of the dark territory of Cassini Regio on Iapetus remains a mystery. Also puzzling is the equatorial ridge that bisects this terrain, and how it fits into the story of the moon's strange brightness dichotomy. The ridge is seen here, curving along the lower left edge of Iapetus.

The view looks down onto the northern hemisphere of Iapetus (1,468 kilometers, or 912 miles across), and shows terrain on the moon's leading hemisphere.

The image was taken in polarized green light with the Cassini spacecraft narrow-angle camera on Nov. 12, 2005 at a distance of approximately 417,000 kilometers (259,000 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 95 degrees. Image scale is about 2 kilometers (1 mile) per pixel.

During its historic close encounter with Phoebe, the Cassini spacecraft captured a series of high resolution images of the small moon, six of which have been put together to create this mosaic.

Phoebe shows an unusual variation in brightness over its surface due to the existence on some crater slopes and floors of bright material - thought to contain ice - on what is otherwise one of the darkest known bodies in the solar system. Bright streaks on the rim of the large crater in the North (up in this image) may have been revealed by the collapse of overlying darker material from the crater wall. The large crater below right-of-center shows evidence of layered deposits of alternating bright and dark material. A possible mechanism for this apparent layering was discussed in an earlier image release.

Hints of Phoebe's irregular topography can be seen peeking out from the shadows near the lower left and upper left parts of the image. These are real features - possibly crater rims or mountain peaks - that are just being hit by the first light of sunrise on Phoebe.

Phoebe's surface shows many large and small-scale craters. The emerging view of Phoebe is that it might have been part of an ancestral population of icy, comet-like bodies, some of which now reside in the Kuiper Belt beyond Neptune. The images in this mosaic were taken in visible light with the narrow-angle camera at distances ranging from 15,974 kilometers (9,926 miles) to 12,422 kilometers (7,719 miles). The image scale is 74 meters (243 feet) per pixel. Contrast in the image has been enhanced slightly to improve visibility.

The Cassini spacecraft looks toward the Saturnian horizon as Dione and Janus glide past.

A few craters are visible on Dione (1,126 kilometers, or 700 miles across). Janus (181 kilometers, or 113 miles across) is slightly blurred due to its motion during the exposure.

The rings appear essentially edge-on in this view, as the Cassini spacecraft continues its recent activities close to the ringplane.

The image was taken with the Cassini spacecraft narrow-angle camera on March 10, 2006, using a filter sensitive to wavelengths of infrared light centered at 750 nanometers. The image was acquired at a distance of approximately 2.9 million kilometers (1.8 million miles) from Saturn. The image scale is 17 kilometers (11 miles) per pixel.

In their orbital ballet, Janus and Epimetheus swap positions every four years -- one moon moving closer to Saturn, the other moving farther away. The two recently changed positions (the swap occurring on Jan. 21, 2006), and Janus will remain the innermost of the pair until 2010, when they will switch positions again.

Although the moons appear to be close in the image, they are not. Janus (181 kilometers, or 113 miles across at right) is about 40,000 kilometers (25,000 miles) farther away from Cassini than Epimetheus (116 kilometers, or 72 miles across, at left) in this view. In fact, even when they are at their closest, tugging at each other and swapping orbital positions, they are never closer than about 15,000 kilometers (9,000 miles).

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 20, 2006 at a distance of approximately 452,000 kilometers (281,000 miles) from Epimetheus and 492,000 kilometers (306,000 miles) from Janus. The image scale is 3 kilometers (2 miles) per pixel on both moons.

Cassini's best close-up view of Saturn's F ring shepherd moon, Pandora, shows that this small ring-moon is coated in fine dust-sized icy material.

Craters formed on this object by impacts appear to be covered by debris, a process that probably happens rapidly in a geologic sense. The grooves and small ridges on Pandora (84 kilometers, or 52 miles across) suggest that fractures affect the overlying smooth material. The crisp craters on another Saturn moon, Hyperion, provide a contrasting example of craters on a small object (see Odd World).

Cassini acquired infrared, green and ultraviolet images on Sept. 5, 2005, which were combined to create this false-color view. The image was taken with the Cassini spacecraft narrow-angle camera at a distance of approximately 52,000 kilometers (32,000 miles) from Pandora and at a Sun-Pandora-spacecraft, or phase, angle of 54 degrees. Resolution in the original image was about 300 meters (1,000 feet) per pixel. The image has been magnified by a factor of two to aid visibility.

Plunging cliffs and towering mountains characterize the gigantic impact structure called Odysseus on Saturn's moon Tethys. The great impact basin lies before the Cassini spacecraft in one of the best views yet obtained.

Quite a few small craters are visible inside Odysseus (450 kilometers, or 280 miles across), making it clear that this is not a very young structure. However, a comparison of cratering density between the interior of Odysseus and the surrounding terrain should show whether the large basin is at least relatively young.

Odysseus is on the leading hemisphere of Tethys (1,071 kilometers, or 665 miles across). North is up and rotated 18 degrees to the right.

The image was taken in polarized ultraviolet light with the Cassini spacecraft narrow-angle camera on Dec. 24, 2005 at a distance of approximately 196,000 kilometers (122,000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 85 degrees. Resolution in the original image was 1 kilometer (3,831 feet) per pixel. The image has been magnified by a factor of two and contrast-enhanced to aid visibility.

A masterpiece of deep time and wrenching gravity, the tortured surface of Saturn's moon Enceladus and its fascinating ongoing geologic activity tell the story of the ancient and present struggles of one tiny world. This is a story that is recounted by imaging scientists in a paper published in the journal Science on March 10, 2006.

The enhanced color view of Enceladus seen here is largely of the southern hemisphere and includes the south polar terrain at the bottom of the image.

Ancient craters remain somewhat pristine in some locales, but have clearly relaxed in others. Northward-trending fractures, likely caused by a change in the moon's rate of rotation and the consequent flattening of the moon's shape, rip across the southern hemisphere. The south polar terrain is marked by a striking set of 'blue' fractures and encircled by a conspicuous and continuous chain of folds and ridges, testament to the forces within Enceladus that have yet to be silenced.

The mosaic was created from 21 false-color frames taken during the Cassini spacecraft's close approaches to Enceladus on March 9 and July 14, 2005. Images taken using filters sensitive to ultraviolet, visible and infrared light (spanning wavelengths from 338 to 930 nanometers) were combined to create the individual frames. The mosaic is an orthographic projection centered at 46.8 degrees south latitude, 188 degrees west longitude, and has an image scale of 67 meters (220 feet) per pixel. The original images ranged in resolution from 67 meters per pixel to 350 meters (1,150 feet) per pixel and were taken at distances ranging from 11,100 to 61,300 kilometers (6,900 to miles) from Enceladus.